This invention relates to blower motors and in particular, to a blower motor for use in a bypass or wet-type vacuum cleaner application.
Blower motors in bypass vacuum cleaners have an impeller which moves air from an inlet to an outlet of an impeller housing fitted to the motor without passing through the motor itself. This construction allows the vacuum cleaner to suck up liquids as well as dust and dirt without damaging the electric motor.
The impeller is mounted on a shaft of the motor. The shaft is journalled in a bearing where it passes through an end bracket of the motor housing which also acts as a divider between the motor and the impeller. The bearing is sealed and an additional seal between the shaft and the end bracket may be provided to prevent air leakage from the impeller housing into the motor proper through the bearing. The fan end bracket separates the motor from the impeller housing and separates the motor from the working air flow of the impeller. One problem is that the fan end bracket has an axial extending annular projection to connect with the stator of the motor. A fan providing air flow for cooling the motor is mounted on the shaft adjacent the fan end bracket. This requires apertures in the annular projection to avoid the use of expensive side core moulding dies. These apertures are provided by axial holes which extend through the outer planar surface of the fan end bracket into the annular projection,. These holes in the end bracket need to be closed in order to seal the impeller chamber from the motor. This has been done conveniently by a diffuser plate. The diffuser plate provides guides for guiding the working air from the impeller to outlet openings in the impeller housing. The diffuser plate has a planar portion which lies over the fan end bracket and covers the openings in the end bracket. This has proved successful in low pressure blowers, but modern bypass blower motors run at a higher speed with more efficient impellers creating a higher pressure environment inside the impeller chamber adjacent the diffuser and end bracket. The high air pressure inside the impeller chamber causes leaking of air between the diffuser plate and the end bracket.
Accordingly, there is a need for an effective yet simple air tight seal between the end bracket and the diffuser plate. This is achieved by the present invention by the use of labyrinth seals, O-ring seals or a combination thereof between the end bracket and the diffuser plate.
Accordingly, the present invention provides a bypass blower motor assembly comprising: a motor including a shaft and a fan end bracket supporting a bearing for the shaft; a diffuser plate fitted to the fan end bracket; an impeller fixed to the shaft for rotation therewith; and an impeller housing fixed to the fan end bracket and accommodating the impeller and diffuser plate, wherein the impeller housing has an inlet and a plurality of outlet openings, the impeller being operated to create an air flow from the inlet to the outlet openings and the diffuser plate having vanes for guiding the air flow from the impeller to the outlet openings, the fan end bracket has a number of openings which are seated by the diffuser plate.